Natural gas is bought and sold based on its heating value. It is the BTU content that determines the monetary value of a given volume of natural gas. This BTU value is generally expressed in decatherms (one million BTU). In the determination of total heat value of a given volume of gas, a sample of the gas is analyzed and from the composition its heat value per unit volume is calculated. This value is generally expressed in BTU/cu ft. The typical range of transmission quality gas ranges between 1000 and 1100 BTU/cu ft. Production gas, storage facility gas, NGL, and new found Shale Gas can have much higher heating values up to or even exceeding 1500 BTU/cu ft.
There has been a long standing controversy between gas producers and gas transporters regarding entrained liquid typically present in most high BTU/cu ft gas (rich or “wet” gas). Transporter tariffs require essentially liquid-free gas, while hydrocarbon liquid in the gas being transported causes operational and safety problems. Accordingly, the practice is to separate the liquid before entering a transport (pipe) line.
The API 14.1 standards (Manual of Petroleum Measurement Standards, 2006) scope does not include supercritical fluid (dense phase) or “wet gas” “(a term referenced by the Natural Gas industry as a gas that is at or below its hydrocarbon dew point temperature and/or contains entrained liquid), nor does the GPA 2166 standard (Obtaining Natural Gas Samples for Analysis by Gas Chromatography, 2005). In short, there is no presently known standard which defines how to obtain a “representative sample” of a natural gas supply having entrained hydrocarbon in any form.
Accordingly, to fully comply with the current industry standards, entrained liquids must be removed when using sample systems. Membrane-tipped probes such as the A+ Corporation Genie Probe (see U.S. Pat. No. 357,304, U.S. Pat. No. 6,701,794, U.S. Pat. No. 6,904,816, U.S. Pat. No. 7,004,041, and U.S. Pat. No. 7,134,318) have been used for many years to shed entrained liquids inside pressurized pipelines to obtain samples or the like. Other companies such as Valtronics, Inc/Mustang Sampling have bolted enclosures to the A+ Corporation membrane-tipped probes, then placing A+ Corporation Genie membrane separators in a second enclosure mounted closer to the analyzer. See, for example, Mayeaux U.S. Pat. No. 6,357,304, Thompson U.S. Pat. No. 7,162,933, Thompson US 2012/0325694 A1 (FIG. 1), as well as Thompson D674,052. Other companies, such as Welker Engineering, use non-membrane probes (fixed “stinger” probes) and bring the liquids outside the pipeline to reject them outside the pipeline, hanging a hinged enclosure onto the probe (see Welker SCHS brochure). Welker and other companies such as PGI install sample pumps and composite samplers and bolt enclosures to the pipeline (see Welker U.S. Pat. No. 5,531,130 and Nimberger U.S. Pat. No. 5,109,709).
Each of these enclosure systems are engineered for one specific configuration, and once the probe housing or pump is installed, it cannot be removed without shutting down and depressurizing the process.
In Thompson U.S. Pat. No. 7,162,933, we see an enclosure which has been believed utilized with a Mayeaux U.S. Pat. No. 6,357,304 probe. The enclosure has mating upper and lower horizontal halves. Welker U.S. Pat. No. 5,531,130 has a similar two half-horizontal approach.
The Welker SCHS brochure depicts a vertical version of the two, half enclosure with a hinged door design. Nimberger U.S. Pat. No. 5,109,709 utilizes a hinged door as well. Thompson US 2012/0325694 A1 attempts to increase access to the probe inside the enclosure by using a diagonal-half approach. While this change may increase accessibility by 20%-30%, it still leaves much to be desired for component access. Further, the pipeline must be shut down and depressurized to install and remove the probe with all the prior art.